This invention relates to gas turbine engines, and more particularly to a ducted turbofan engine having the bulky, static portions of the engine directly supported from an aircraft, and the power generating portion of the engine capable of being removable from the rest of the engine.
Engines are expensive and difficult to service and install in aircraft. Part of the high maintenance costs on the engines is the fact that it is necessary to remove the entire engine from the aircraft for servicing. This is of special significance in a ducted turbofan engine where the diameter of the fans may be as much as 12-14 feet and the weight of the frame and outer fan cowl becomes quite substantial. The cost and difficulty of the removal of such large and bulky engines is often great.
In a ducted turbofan engine, the engine itself is supported by the aircraft pylon. A large fan frame mounts the fan cowl to the engine. Typically, the fan inlet, the aft fan duct, and often the thrust reverser, are all integrated with the cowl and result in a bulky, expensive, and exceedingly large part of the engine which is supported by the power generating portion of the engine through the frame. Likewise, the fan stator vanes are also supported by the power generating portion of the engine and also add considerable bulk. These parts normally require infrequent servicing and such servicing can be done right on the aircraft.
In servicing the power generating portion of the engine, the entire engine must be removed from the aircraft including the fan cowl, the fan frame, the stator vanes, and all other parts supported by the core engine. The items requiring off engine servicing are normally the internal parts of the power generating portion.
It has been known to split the nacelle and thrust reverser which is directly around the power generating portion of the engine. However, this is typically a lightweight sheet metal covering which easily splits to expose the machinery and equipment of the power generating portion of the engine. On the other hand, the static engine parts such as the fan cowl, fan stator, inlet, aft fan duct, and other parts, are all integrated with and supported by the power generating portion of the engine through the structural fan frames and are never split and are therefore removed with the power generating portion of the engine.
As ducted turbofan engines continue to get larger to provide increased thrust, the need to reduce the cost, time and effort for removing the entire engine for servicing, transport, and maintenance, increases.